1. Field of the Invention
The present invention relates to a light emitting diode array, and in particular to a light emitting diode array usable for data-back units of, for example, printer heads and cameras.
2. Description of the Related Art
A conventional light emitting diode array and a method for producing the same are disclosed in, for example, Japanese Laid-Open Publication No. 8-64864 filed by Sharp Kabushiki Kaisha and entitled "Light-Emitting Diode Array and Method for Fabricating the Same" (corresponding U.S. patent application Ser. No. 08/516,409). The light emitting diode array disclosed in the above-mentioned publication is shown in FIGS. 7 through 10.
FIG. 7 is a plan view of the conventional light emitting diode array. The light emitting diode array has seven light emitting elements 100. FIG. 8 is a plan view of one of the light emitting elements 100, and FIG. 9 is a cross-sectional view of the light emitting element 100 taken along lines IX--IX in FIG. 8. FIG. 10 is a partial isometric view of the light emitting diode array shown in FIGS. 7 through 9.
As best shown in FIG. 9, the light emitting element 100 includes an n-type GaAs substrate 50, an n-type GaAs buffer layer 51, an n-type Al.sub.0.5 In.sub.0.5 P cladding layer 52, an undoped (Al.sub.0.3 Ga.sub.0.7).sub.0.5 In.sub.0.5 P active layer 53, a p-type Al.sub.0.5 In.sub.0.5 P cladding layer 54, and an Al.sub.0.7 Ga.sub.0.3 As current diffusion layer 55. The layers 51 through 55 are sequentially provided on the n-type GaAs substrate 50 in this order and formed by MOCVD.
The light emitting element 100 further includes an insulative layer 56 provided on the current diffusion layer 55. The insulative layer 56 is formed by forming an SiN.sub.x layer by plasma CVD on the current diffusion layer 55 and then performing photolithography and etching using buffered hydrogen fluoride. The insulative layer 56 is provided for preventing an electric current from being injected below a bonding pad 59 described below.
The light emitting element 100 further includes a p-side electrode 57 formed of a Ti/AuZn material and provided on the current diffusion layer 55 so as to cover the insulative layer 56, an n-side electrode 58 formed of an AuGe/Ni material and provided on a rear surface of the substrate 50, and the bonding pad 59 provided on the p-side electrode 57 preferably by sputtering Ti/Au. Red light mainly comes out from an area 155 of the current diffusion layer 55 on which the insulative layer 56 is not formed.
The conventional light emitting diode shown in FIGS. 7 through 10 includes the current diffusion layer 55 in an area where it is not desirable to cause light to pass, namely, an area other than the area 155. Accordingly, a light emission driving current expands through the current diffusion layer, and thus light passes an area where light passage is not desired. That is, the current diffusion layer acts as a light guide, thus causing light to pass an area where light passage is not desired. As a result, the light emitting point of each light emitting element is blurred.